This invention relates generally to systems, components, and methods for providing lubrication in a subterranean environment, such as in a well or in underground utility work. A particular aspect of the invention relates to an extended-lubrication downhole motor.
Various subterranean operations require there to he movement between parts that need to be lubricated for one or more reasons (for example, to facilitate movement, to reduce frictional heating). The lubricant in these uses tends to degrade or be used up as the operation in which the lubrication is needed continues. On-going replenishment of the lubricant would be desirable to prolong the operating time. Although this need may exist in various subterranean uses, one particular use is in downhole motors that may be used in underground utility work or in drilling wells, for example. The following explanation refers to such use in an oil or gas well; however, the present invention is not limited in its broader aspects to this particular use or environment.
One kind of movement that may occur between parts in a tubing string that has been lowered into a well is rotary motion. One example of such rotary motion is that which occurs during drilling a well using coiled tubing and a downhole motor attached in the coiled tubing string. A housing connected to the coiled tubing acts as a stator of the downhole motor, inside of which is a rotor to which the drill bit is connected. A bearing pack is connected between the rotor and the connected working implement (the drill bit in this example). The bearing pack is filled with a lubricant to reduce friction and heating as the rotor rotates inside the stator in response to drilling fluid being pumped through the coiled tubing and the downhole motor.
A conventional coiled tubing downhole motor as just described may operate until the lubricant is sufficiently used up (for example, by thinning and migrating around the seals and out of the sealed region). So, one limitation on how long a downhole motor of this type can be used in the well is how long sufficient lubricant can be retained in the bearing pack before the tubing string needs to be withdrawn from the well and the bearing pack repaired or replaced. Pulling the coiled tubing string out of the well, repairing or replacing the bearing pack, and again running the tubing string back into the well are time consuming and costly. To reduce such time and cost, there is the need for an improved downhole lubrication system and method and components for such system and method whereby longer downhole working times can be obtained so that, for the above example, fewer, less frequent trips out of the well are needed. There is a particular need for an extended-lubrication downhole motor. Although I am aware of a type of drill bit that moves lubricant from one or more supplies in the bit in response to the rotational force as the bit is rotated, my invention is distinguishable in satisfying the aforementioned needs.
The present invention overcomes the above-noted and other shortcomings of the prior art, and meets the aforementioned needs, by providing for novel and improved lubrication replenishment downhole in a subterranean environment by way of the novel and improved system, components, and method of the present invention. In addition to the advantage of providing lubrication replenishment in a subterranean environment, the present invention has the advantage of providing such lubrication automatically (that is, without control from the surface apart from providing basic operation of the tool, such as a pressurized flow of fluid into a downhole motor). Such automatic lubrication replenishment is provided in a relatively simple, relatively low maintenance manner such that extended tool operating times can be obtained. Still another advantage is that such replenishment can be incorporated to provide a novel and improved extended-lubrication downhole motor, and preferably one which can operate downhole longer than previous conventional types of downhole motors. The invention can be used in various fields, including without limitation the oil and gas industry and the various utility (for example, electrical power, gas, communications) industries.
The present invention provides a downhole lubrication system comprising a lubricant ejector having a reservoir defined in it to hold replenishment lubricant. The lubricant injector includes a driver to move at least a portion of the replenishment lubricant out of the reservoir in response to a pressure from a flowing fluid. The lubricant ejector is defined to be moved downhole with apparatus requiring lubrication and having a lubrication chamber. Also included in the downhole lubrication system is a flow coupler connected to the lubricant ejector such that the flow coupler channels to the tool""s lubrication chamber replenishment lubricant moved out of the reservoir in response to operation of the driver.
In a particular implementation, the downhole lubrication system includes a downhole lubricant applicator comprising lubricant and a rotor for a downhole motor, wherein the rotor has a longitudinal bore holding the lubricant. The longitudinal bore has a first end through which to receive a force to move at least a portion of the lubricant out a second end of the longitudinal bore. This downhole lubricant applicator may further comprise a flow coupler connected to the rotor. The flow coupler has a channel defined with a port communicating with the second end of the longitudinal bore. The channel also has another port, this one communicating with an outer lubrication chamber of a bearing pack of the downhole motor.
A particular component for the flow coupler includes a flow diverter comprising an inner body having an upper end for connecting to the rotor of a downhole motor and having a lower end for connecting to a bearing pack of the downhole motor. Defined in the inner body are an upper cavity extending into the inner body from the upper end, a lower cavity extending into the inner body from the lower end, an upper aperture communicating with the lower cavity, and a lower aperture communicating with the upper cavity. The inner body further includes a seal bearing surface disposed between the upper and lower apertures. The flow diverter may further comprise a housing having the inner body disposed therein and a seal disposed between the seal bearing surface and an inner surface of the housing. In a particular implementation, the upper aperture and the lower cavity are configured to conduct a flow of drilling fluid pumped through a tubing string, and the upper cavity and the lower aperture are configured to conduct a flow of replenishment lubricant from the rotor to the bearing pack, when the flow diverter is connected into the tubing string with the downhole motor.
Another component for the flow coupler is a flex coupling having a passageway that communicates between the rotor and the flow diverter.
The present invention also provides a downhole motor, comprising: a stator; a rotor disposed in the stator; replenishment lubricant disposed in a reservoir defined within the downhole motor; and a bearing pack connected to the stator, the rotor and the reservoir of replenishment lubricant such that replenishment lubricant moves into the bearing pack from the reservoir as the downhole motor operates.
The present invention more particularly provides an extended-lubrication downhole motor. This downhole motor comprises a stator configured to connect in a tubing string. It also comprises a rotor disposed in the stator such that the rotor rotates in response to fluid pumped through the stator from the tubing string, the rotor having an axial bore. The downhole motor further comprises lubricant disposed in the axial bore and a piston disposed in the axial bore above the lubricant. A plug having an orifice defined in it is connected to the rotor such that pressure from the pumped fluid communicates through the orifice and acts against the piston. A bearing pack of the downhole motor is connected to a flow coupler of the downhole motor, which flow coupler is also connected to the rotor. The connection of the flow coupler to the rotor and the bearing pack is such that the flow coupler communicates to the bearing pack lubricant pushed out of the rotor in response to movement of the piston toward the lubricant in the rotor in response to pressure from the pumped fluid communicated through the orifice. In a particular implementation, the bearing pack has a longitudinal flow passageway to conduct motive fluid that has flowed along the exterior of the rotor, and the bearing back has a lubricant chamber disposed radially outwardly from the longitudinal flow passageway. In such implementation the flow coupler includes a flow diverter having a body connected to the rotor and the bearing pack. This flow coupler also has a seal disposed on the body. The body has a first channel communicating with the axial bore of the rotor above the seal and with the lubricant chamber of the bearing pack below the seal. The body has a second channel communicating with the exterior of the body above the seal and with the longitudinal flow passageway of the bearing pack below the seal. The flow coupler may further include a flex shaft connected to the rotor and the body of the flow diverter, with the flex shaft having a passage defined through it to provide a lubricant flow path between the axial bore of the rotor and the first channel in the body.
The present invention also provides a method of replenishing lubricant in a downhole motor. This method comprises injecting replenishment lubricant from a reservoir of replenishment lubricant in the downhole motor into a bearing pack of the downhole motor as the downhole motor operates.
The present invention also provides a method of replenishing lubricant in a downhole motor. This definition of the present invention comprises: operating a downhole motor disposed in a subterranean environment, including pumping fluid into the downhole motor; moving lubricant from a reservoir in a rotor of the downhole motor, including communicating a pressure responsive to the pumped fluid against a piston disposed in the reservoir with the lubricant; and cross-channeling moved lubricant and pumped fluid within the downhole motor, including conducting moved lubricant from the reservoir to a bearing pack of the downhole motor and conducting pumped fluid from outside the rotor to a passageway through the bearing pack.
Therefore, from the foregoing, it is a general object of the present invention to provide for novel and improved lubrication replenishment downhole in a subterranean environment by way of the novel and improved system, components, and method of the present invention, one particular embodiment of which includes an extended-lubrication downhole motor. Other and further objects, features and advantages of the present invention will be readily apparent to those skilled in the art when the following description of the preferred embodiments is read in conjunction with the accompanying drawings.